Verilog Code

10M11D5716 SIMULATION LAB

1

EXPERIMENT: 1 LOGIC GATES

AIM: To design all the logic gates using dataflow modeling style and verify the

functionalities along with their synthesis and simulation reports.

TOOLS USED: Xilinx 9.2i Hardware Tool.

DESCRIPTION OF THE MODULE:

NOT GATE: Not is a unary operator. It is also called as an Inverter .The output is the

complement of the input.

AND GATE: The output of the AND gate is logic one only when all the inputs are equal

to logic one .An N-input and gate has N inputs and 1 output.

OR GATE: Or gate output is logic one if any one of the inputs to the gate is logic one.

N-input or gate has N inputs and 1output.

NAND GATE: NAND gate output is logic 1 when any one of the input is logic 0.An N-

input NAND gate has N inputs and one output. NAND gate is identical to and gate

connected to an inverter.

NOR GATE: NOR gate is nothing but a combination of OR gate and INVERTER .NOR

gate output is logic one only when all the inputs are equal to logic zero. An N- input

NOR gate is having N inputs and one output.

XOR GATE: The output of XOR gate is logic zero when all the inputs are same.

XNOR GATE: The output of XNOR gate is logic one only when both the inputs are at

logic one. XNOR gate is nothing but the XOR gate followed by an INVERTER.

TRUTH TABLE:

a b Y[0]

(not)

Y[1]

(and)

Y[2]

(or)

Y[3]

(nand)

Y[4]

(nor)

Y[5]

(xor)

Y[6]

(xnor)

0 0 1 0 0 1 1 0 1

0 1 1 0 1 1 0 1 0

1 0 0 0 1 1 0 1 0

1 1 0 1 1 0 0 0 1


2

VERILOG CODE:

LOGIC GATES USING DATAFLOW MODELING STYLE

`resetall

`timescale 1ns / 1ps module logicgate_df(a, b, y);

input a,b; // input declarations

output [0:6]y; //output declarations

wire a,b; //input as wires

assign y[0] = ~a; //not gate

assign y[1] = a&b; //and gate

assign y[2] = a|b; //or gate

assign y[3] = ~(a&b); //nand gate

assign y[4] = ~(a|b); //nor gate

assign y[5] = a^b; //xor gate

assign y[6] = ~(a^b); //xnor gate

endmodule

LOGIC GATES TEST BENCH

`resetall

`timescale 1ns/1ps

module logicgate_df_tb_v;

// Inputs reg a; reg b; // Outputs wire [0:6] y; // Instantiate the Unit Under Test (UUT) logicgate_df uut ( .a(a), .b(b), .y(y) ); initial begin a = 0; b = 0;


3

#10 a = 0; b = 1; #10 a = 1; b = 0; #10 a = 1; b = 1; end initial begin #50 $finish; end endmodule

SYNTHESIS RESULTS:


4

SIMULATION RESULTS:

CONCLUSION: Basic logic gates NOT, AND, OR, NOR, NAND, XOR, XNOR are designed in dataflow,

behavioral models and outputs are verified using test bench.


5

EXPERIMENT: 2 ADDERS

2.1. HALF ADDER

AIM: To design a half adder along with a verilog code in the dataflow model and verify

its functionality and check its simulation report.

TOOLS USED: Xilinx 9.2i Hardware Tool


A combinational circuit that performs the addition of two bits is called half adder.The

half adder operation needs two binary inputs (augends and addend bits)and two binary

outputs (sum and carry). The sum can range from 0 to 2 which require two bits to

express. The lower order bit may be named as half sum and the higher order bit may be

named as carry.

BLOCK DIAGRAM:

TRUTH TABLE:

a b carry Sum

0 0 0 0

0 1 0 1

1 0 0 1

1 1 1 0

a, b are inputs and carry, sum are outputs


6

VERILOG CODE: HALF ADDER USING DATAFLOW MODELING STYLE

`resetall

`timescale 1ns/1ps

module halfadder(a, b, sum, carry);

input a;

input b;

output sum;

output carry;

wire a,b;

assign sum= a^b;

assign carry=a&b;

endmodule

HALF ADDER TEST BENCH

`resetall

`timescale 1ns/1ps

module halfadder_bh_tb_v;

// Inputs

reg a;

reg b;

// Outputs

wire sum;

wire carry;

// Instantiate the Unit Under Test (UUT)

halfadder_beh uut (

.a(a),

.b(b),

.sum(sum),

.carry(carry)

);


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initial begin

// Initialize Inputs

a = 0;

b = 0;

#20 a=0; b=1;

#20 a=1; b=0;

#20 a=1; b=1;

end

initial

begin

#100 $finish;

end

endmodule

SYNTHESIS RESULTS:


8

SIMULATION RESULTS:

CONCLUSION:

HALF ADDER is designed in behavioral and dataflow styles and output is verified

through a test bench.


9

2.2 FULL ADDER

AIM: To design a FULL ADDER along with a verilog code in behavioral and dataflow

the two models and verify its functionality and check its simulation report.

TOOLS USED: Xilinx 9.2i Hardware Tool


The FULL ADDER is a combinational circuit that performs the arithmetic sum of three

input bits. It consists of three inputs and two outputs. A FULL ADDER can also be

implemented using two HALF ADDERS and one OR gate.

BLOCK DIAGRAM:

TRUTH TABLE:

A B C Sum Carry

0 0 0 0 0

0 0 1 1 0

0 1 0 1 0

0 1 1 0 1

1 0 0 1 0

1 0 1 0 1

1 1 0 0 1

1 1 1 1 1

Where a, b, cin are the inputs and sum, carry are outputs


10

VERILOG CODE: FULL ADDER USING DATAFLOW MODELING STYLE

`resetall

`timescale 1ns/1ps

module fulladder_dt(a, b, c, sum, carry); input a; input b; input c; output sum; output carry; wire a,b; assign sum=a^b^c; assign carry=(a&b)|(b&c)|(c&a); endmodule

FULL ADDER TEST BENCH

`resetall

`timescale 1ns/1ps

module fulladder_beh_tb_v;

// Inputs

reg a;

reg b;

reg c;

// Outputs

wire sum;

wire carry;


fulladder_beh uut (

.a(a),

.b(b),

.c(c),

.sum(sum),


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.carry(carry)

);

initial begin


a=0; b=0;c =0;

#20 a=0; b=0; c=1;

#20 a=0; b=1; c=0;

#20 a=0; b=1; c=1;

#20 a=1; b=0; c=0;

#20 a=1; b=0; c=1;

#20 a=1; b=1; c=0;

#20 a=1; b=1; c=1;

end

initial

begin

#220 $finish;

end

endmodule


12

SYNTHESIS RESULTS:

SIMULATION RESULTS:

CONCLUSION:

FULL ADDER is designed in behavioral and dataflow styles and output is verified

through a test bench.


13

4-BIT BINARY PARALLEL ADDER

AIM: To design a 4-BIT BINARY PARALLEL ADDER in the behavioral model and

verify its functionality and check its simulation report.

TOOLS USED:Xilinx 9.2i Hardware Tool

DESCRIPTION OF THE MODULE: 4 bit binary parallel adder adds four bit binary

numbers. The binary parallel adder is a digital function that produces the arithmetic sum

of two binary numbers in parallel. It consists of full adders connected in cascade, with the

output carry of one full adder connected to the input carry of the next full adder.

BLOCK DIAGRAM:

A[3] B[3] A[2] B[2] A[1] B[1] A[0] B[0] Ci S[3] S[2] S[1] S[0] S[3] S[2] S[1] S[0]

FULL

ADDER

FULL

ADDER

FULL

ADDER

FULL

ADDER

Co


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TRUTH TABLE:

A B Ci S Co Ci S Co

0000 0000 0 0000 0 1 0001 0

0001 0001 0 0010 0 1 0011 0

0010 0010 0 0100 0 1 0101 0

0011 0011 0 0110 0 1 0111 0

0100 0100 0 1000 0 1 1001 0

0101 0101 0 1010 0 1 1011 0

0110 0110 0 1100 0 1 1101 0

0111 0111 0 1110 0 1 1111 0

1000 1000 0 0000 1 1 0001 1

1001 1001 0 0010 1 1 0011 1

1010 1010 0 0100 1 1 0101 1

1011 1011 0 0110 1 1 0111 1

1100 1100 0 1000 1 1 1001 1

1101 1101 0 1010 1 1 1011 1

1110 1110 0 1100 1 1 1101 1

1111 1111 0 1110 1 1 1111 1

Where a,b,cin are the inputs and sum,carry are outputs VERILOG CODE:

4-BIT BINARY PARALLEL ADDER USING BEHAVIORAL MODELING

`resetall

`timescale 1ns/1ps

module bit4pladbh(a,b,ci,s,co) ; input [0:3]a; input [0:3]b; input ci;


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output [0:3]s; output co; wire [0:3]a; wire [0:3]b; wire ci; reg [0:3]s; reg co; always@(a or b or ci) begin if(ci==1'b0) begin case({a,b}) 8'b00000000: begin s=4'b0000; co=1'b0;end 8'b00010001: begin s=4'b0010; co=1'b0;end 8'b00100010: begin s=4'b0100; co=1'b0;end 8'b00110011: begin s=4'b0110; co=1'b0;end 8'b01000100: begin s=4'b1000; co=1'b0;end 8'b01010101: begin s=4'b1010; co=1'b0;end 8'b01100110: begin s=4'b1100; co=1'b0;end 8'b01110111: begin s=4'b1110; co=1'b0;end 8'b10001000: begin s=4'b0000; co=1'b1;end 8'b10011001: begin s=4'b0010; co=1'b1;end 8'b10101010: begin s=4'b0100; co=1'b1;end 8'b10111011: begin s=4'b0110; co=1'b1;end 8'b11001100: begin s=4'b1000; co=1'b1;end 8'b11011101: begin s=4'b1010; co=1'b1;end 8'b11101110: begin s=4'b1100; co=1'b1;end 8'b11111111: begin s=4'b1110; co=1'b1;end endcase end else begin case({a,b}) 8'b00000000: begin s=4'b0001; co=1'b0;end 8'b00010001: begin s=4'b0011; co=1'b0;end 8'b00100010: begin s=4'b0101; co=1'b0;end 8'b00110011: begin s=4'b0111; co=1'b0;end 8'b01000100: begin s=4'b1001; co=1'b0;end 8'b01010101: begin s=4'b1011; co=1'b0;end 8'b01100110: begin s=4'b1101; co=1'b0;end 8'b01110111: begin s=4'b1111; co=1'b0;end 8'b10001000: begin s=4'b0001; co=1'b1;end 8'b10011001: begin s=4'b0011; co=1'b1;end 8'b10101010: begin s=4'b0101; co=1'b1;end 8'b10111011: begin s=4'b0111; co=1'b1;end 8'b11001100: begin s=4'b1001; co=1'b1;end


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8'b11011101: begin s=4'b1011; co=1'b1;end 8'b11101110: begin s=4'b1101; co=1'b1;end 8'b11111111: begin s=4'b1111; co=1'b1;end endcase end end endmodule

BIT 4 BINARY PARALLEL ADDER TEST BENCH

`resetall

`timescale 1ns/1ps

module bit4plabh_tb_v; // Inputs reg [0:3] a; reg [0:3] b; reg ci; // Outputs wire [0:3] s; wire co; // Instantiate the Unit Under Test (UUT) bit4pladbh uut ( .a(a), .b(b), .ci(ci), .s(s), .co(co) ); initial begin a = 4'b0000; b=4'b0000; ci=1'b0; #5 a = 4'b0001; b=4'b0001; ci=1'b0; #5 a = 4'b0010; b=4'b0010; ci=1'b0; #5 a = 4'b0011; b=4'b0011; ci=1'b0; #5 a = 4'b0100; b=4'b0100; ci=1'b0; #5 a = 4'b0101; b=4'b0101; ci=1'b0; #5 a = 4'b0110; b=4'b0110; ci=1'b0; #5 a = 4'b0111; b=4'b0111; ci=1'b0; #5 a = 4'b1000; b=4'b1000; ci=1'b0; #5 a = 4'b1001; b=4'b1001; ci=1'b0; #5 a = 4'b1010; b=4'b1010; ci=1'b0; #5 a = 4'b1011; b=4'b1011; ci=1'b0;


17

#5 a = 4'b1100; b=4'b1100; ci=1'b0; #5 a = 4'b1101; b=4'b1101; ci=1'b0; #5 a = 4'b1110; b=4'b1110; ci=1'b0; #5 a = 4'b1111; b=4'b1111; ci=1'b0; #5 a = 4'b0000; b=4'b0000; ci=1'b1; #5 a = 4'b0001; b=4'b0001; ci=1'b1; #5 a = 4'b0010; b=4'b0010; ci=1'b1; #5 a = 4'b0011; b=4'b0011; ci=1'b1; #5 a = 4'b0100; b=4'b0100; ci=1'b1; #5 a = 4'b0101; b=4'b0101; ci=1'b1; #5 a = 4'b0110; b=4'b0110; ci=1'b1; #5 a = 4'b0111; b=4'b0111; ci=1'b1; #5 a = 4'b1000; b=4'b1000; ci=1'b1; #5 a = 4'b1001; b=4'b1001; ci=1'b1; #5 a = 4'b1010; b=4'b1010; ci=1'b1; #5 a = 4'b1011; b=4'b1011; ci=1'b1; #5 a = 4'b1100; b=4'b1100; ci=1'b1; #5 a = 4'b1101; b=4'b1101; ci=1'b0; #5 a = 4'b1110; b=4'b1110; ci=1'b1; #5 a = 4'b1111; b=4'b1111; ci=1'b1; end initial begin #200 $finish; end endmodule


18

SYNTHESIS RESULTS:


19

SIMULATION RESULTS:

CONCLUSION:

4 BIT BINARY PARALLEL ADDER is designed in behavioral style and output is

verified through a test bench.


20

EXPERIMENT: 4 DECODERS

4.1---- 2 TO 4 LINE DECODER AIM: To design a 2x4 decoder and to write its verilog code in dataflow, behavioral

models, verify the functionality and its output in the simulation report



A decoder is a combinational circuit that converts binary information from n input lines

to a maximum of unique output lines. The purpose of decoder is to generate ( or

less) minterms of n input variables. A 2 to 4 decoder generates all the minterms of two

input variables. Exactly one of the output lines will be one for each combination of values

of input variables.

BLOCK DIAGRAM

TRUTH TABLE:

a b D0 D1 D2 D3

0 0 1 0 0 0

0 1 0 1 0 0

1 0 0 0 1 0

1 1 0 0 0 1

Here a,b are two inputs and D0,D1,D2,D3 denote the outputs of the decoder which

implies minterms of two input variables.


21

VERILOG CODE:

2X4 DECODER USING DATA FLOW MODELING STYLE

`resetall

`timescale 1ns/1ps

module decoder24df(a, b, y);

input a;

input b;

output [0:3] y;

wire a,b;

assign y[0]=(~a) & (~b);

assign y[1]=(~a)& (b);

assign y[2]=(a) & (~b);

assign y[3]= a & b;

endmodule

2 TO 4 LINE DECODER TEST BENCH:

`resetall

`timescale 1ns/1ps

module decoder24_tb_v;

// Inputs

reg a;

reg b;

// Outputs

wire [0:3] y;


decoder24df uut (

.a(a),

.b(b),

.y(y)

);


22

initial begin


a=0;b=0;

#10 a=0; b=1;

#10 a=1; b=0;

#10 a=1; b=1;

end

initial

begin

#60 $finish;

end

endmodule

SYNTHESIS RESULTS:


23

SIMULATION RESULTS:

CONCLUSION: 2 to 4 decoder has been designed using behavioral, dataflow models

are verified using Test Bench.


24

4.2-----3X8 LINE DECODER

AIM: To design a 3*8 decoder and to write its verilog code in dataflow, behavioral

models, verify the functionality and its out put in the simulation report



A Decoder is a multiple-input ,multiple –output logic circuits and converts the coded

input into coded outputs ,the input and output codes are different. The input has fewer

bits than the output code. In 3 to 8 decoder 3 inputs are decoded into 8 outputs.

BLOCK DIAGRAM:

TRUTH TABLE:

a b c D0 D1 D2 D3 D4 D5 D6 D7

0 0 0 1 0 0 0 0 0 0 0

0 0 1 0 1 0 0 0 0 0 0

0 1 0 0 0 1 0 0 0 0 0

0 1 1 0 0 0 1 0 0 0 0

1 0 0 0 0 0 0 1 0 0 0

1 0 1 0 0 0 0 0 1 0 0

1 1 0 0 0 0 0 0 0 1 0

1 1 1 0 0 0 0 0 0 0 1


25

Here a,b,c are the inputs and D0 to D7 are the outputs.

3TO8 LINE DECODER USING DATA FLOW MODELING STYLE

`resetall

`timescale 1ns/1ps

module dec38data (a,b,c,dout);

input a,b,c;

output [0:7]dout;

assign dout[0]=(~a)&(~b)&(~c);

assign dout[1]=(~a)&(~b)&c;

assign dout[2]=(~a)&b&(~c);

assign dout[3]=(~a)&b&c;

assign dout[4]=a&(~b)&(~c);

assign dout[5]=a&(~b)&c;

assign dout[6]=a&b&(~c);

assign dout[7]=a&b&c;

endmodule

3 TO 8 DECODER USING BEHAVIORAL MODELING STYLE

`resetall

`timescale 1ns/1ps

module decoder38beh(a, b, c, y);

input a;

input b;

input c;

output [0:7] y;

reg [0:7]y;

// wire a,b,c;

always@(a or b or c)

begin


26

case({a,b,c})

3'b000:begin y=8'b10000000; end

3'b001:begin y=8'b01000000; end

3'b010:begin y=8'b00100000; end

3'b011:begin y=8'b00010000; end

3'b100:begin y=8'b00001000; end

3'b101:begin y=8'b00000100; end

3'b110:begin y=8'b00000010; end

3'b111:begin y=8'b00000001; end

default :begin y=8'b00000000; end

endcase

end

endmodule

3 TO 8 LINE DECODER TEST BENCH

`resetall

`timescale 1ns/1ps

module decoder38beh_tb_v;

// Inputs

reg a;

reg b;

reg c;

// Outputs

wire [0:7] y;


decoder38beh uut (

.a(a),

.b(b),

.c(c),

.y(y)

);

initial


27

begin


a =0;b=0;c=0;

#10 a=0; b=0; c=1;

#10 a=0; b=1; c=0;

#10 a=0; b=1; c=1;

#10 a=1; b=0; c=0;

#10 a=1; b=0; c=1;

#10 a=1; b=1; c=0;

#10 a=1; b=1; c=1;

end

initial

begin

#100 $finish;

end

endmodule


28

SYNTHESIS RESULTS:


29

SIMULATION RESULTS:

CONCLUSION:3 to 8 line decoder has been designed using different modeling styles

and is verified using the Test Bench.

EXPERIMENT: 5 ENCODERS

5.1------4: 2 LINE ENCODER

AIM: To design a 4:2 line encoder using behavioral and data flow modeling styles and

verified using the test bench TOOLS USED: Xilinx 9.2i Hardware Tool.


An encoder is a digital circuit that performs the inverse operation of the decoder. It has

inputs and n outputs.

BLOCK DIAGRAM:


30

TRUTH TABLE:

din[0] din[0] din[0] din[0] a b

1 0 0 0 0 0

0 1 0 0 0 1

0 0 1 0 1 0

0 0 0 1 1 1

Here din[0],din[1],din[2],din[3] are the inputs and the a,b are the outputs.

VERILOG CODE:

4 TO 2 LINE ENCODER USING BEHAVIORAL MODEL `resetall

`timescale 1ns/1ps

module encoder42beh(din, a, b);

input [0:3] din;

output a;

output b;

reg a;

reg b;

always@(din)

begin

case({din})

4'b1000:begin a=1'b0; b=1'b0; end

4'b0100:begin a=1'b0; b=1'b1; end

4'b0010:begin a=1'b1; b=1'b0; end


31

4'b0001:begin a=1'b1; b=1'b1; end

endcase

end

endmodule

4TO2 LINE ENCODER USING DATAFLOW MODELING STYLE:

`resetall

`timescale 1ns/1ps

module encoder42data(din,a,b) ;

input [0:3]din;

output a,b;

assign a=(din[2])|(din[3]);

assign b=(din[1])|(din[3]);

endmodule

4TO 2 LINE ENCODER TEST BENCH

`resetall

`timescale 1ns/1ps

module encoder42beh_tb_v;

// Inputs

reg [0:3] din;

// Outputs

wire a;

wire b;


encoder42beh uut (

.din(din),

.a(a),

.b(b)

);

initial


32

begin


din=4'b1000;

#10 din=4'b0100;

#10 din=4'b0010;

#10 din=4'b0001;

end

initial

begin

#50 $finish;

end

endmodule

SYNTHESIS RESULTS:


33

SIMULATION RESULTS:

CONCLUSION: A 2 to 4 line encoder has been designed using different modeling styles and is verified using test bench.

5.2---8 : 3 LINE ENCODER

AIM: To design a 8 : 3 line encoder using behavioral and data flow modeling styles and

verified using the test bench. TOOLS USED: Xilinx 9.2i Hardware Tool


An encoder is a digital circuit that performs the inverse operation of the decoder. It has

inputs and n outputs.

BLOCK DIAGRAM:


34

TRUTH TABLE:

din0 din1 din2 din3 din4 din5 din6 din7 a b c

1 0 0 0 0 0 0 0 0 0 0

0 1 0 0 0 0 0 0 0 0 1

0 0 1 0 0 0 0 0 0 1 0

0 0 0 1 0 0 0 0 0 1 1

0 0 0 0 1 0 0 0 1 0 0

0 0 0 0 0 1 0 0 1 0 1

0 0 0 0 0 0 1 0 1 1 0

0 0 0 0 0 0 0 1 1 1 1

Where din0 to din7 are inputs and a,b,c are outputs.

VERILOG CODE:

8 TO 3 ENCODER USING DATAFLOW MODELING STYLE

`resetall

`timescale 1ns/1ps

module encoder83df(din, a, b, c);

input [0:7] din;

output a;

output b;

output c;


35

assign a=din[4] | din[5] | din[6] | din[7];

assign b=din[2] | din[3] | din[6] | din[7];

assign c=din[2] | din[4] | din[6] | din[7];

endmodule

8 TO 3 ENCODER USING BEHAVIORAL MODELING STYLE

`resetall

`timescale 1ns/1ps

module encodr83bh (din,a,b,c);

input [0:7]din;

output a,b,c;

reg a,b,c;

always@(din)

begin

case(din)

8'b10000000:begin a=1'b0;b=1'b0,c=1'b0;end

8'b01000000:begin a=1'b0;b=1'b0;c=1'b1;end







default :begin a=1'bz;b=1'bz;c= 1'b1;end

endcase

end

endmodule

8 TO 3 LINE ENCODER TEST BENCH:

`resetall


36

`timescale 1ns/1ps

module encoder83df_tb_v;

// Inputs

reg [0:7] din;

// Outputs

wire a;

wire b;

wire c;


encoder83df uut (

.din(din),

.a(a),

.b(b),

.c(c)

);

initial

begin


din=8'b10000000;

#10 din=8'b01000000;

#10 din=8'b00100000;

#10 din=8'b00010000;

#10 din=8'b00001000;

#10 din=8'b00000100;

#10 din=8'b00000010;

#10 din=8'b00000001;

end

initial

begin


37

#100 $finish;

end

endmodule

SYNTHESIS RESULTS:

SIMULATION RESULTS:


38

CONCLUSION: 8 to 3 line encoder has been designed using behavioral and data flow modeling styles

and verified using the test bench.

EXPERIMENT: 6 MULTIPLEXER

6.1---4:1 MULTIPLEXER


39

AIM: To design a 4:1 multiplexer using behavioral, dataflow models and verify its

functionality using the test bench.



A multiplexer has a group of data inputs and a group of control inputs. It is also called as

data selector. The control inputs are used to select one of the data inputs and connect it to

the output terminal. A 4:1 mutliplexer has four inputs ,2 selection line and 1 output.

BLOCK DIAGRAM:

TRUTH TABLE:

S1 S0 Y

0 0 din[0]

0 1 din[1]

1 0 din[2]

1 1 din[3]

VERILOG CODE:

4:1 MUX USING DATA FLOW MODELING STYLE:

`resetall

`timescale 1ns/1ps

module mux41data (din,s,y);

input [0:3] din;

input[0:1]s;

output out;

assign out=din[s];


40

endmodule

4:1 MUX USING BEHAVIORAL MODELING STYLE:

`resetall

`timescale 1ns/1ps

module mux42beh(din, s0, s1, y);

input [0:3] din;

input s0;

input s1;

output y;

reg y;

wire s0,s1;

always@(s0 or s1)

begin

case({s0,s1})

2'b00:y=din[0];

2'b01:y=din[1];

2'b10:y=din[2];

2'b11:y=din[3];

default:y=1'b1;

endcase

end

endmodule

4:1 MUX TEST BENCH:

`resetall

`timescale 1ns/1ps

module mux42beh_tb_v;

// Inputs

reg [0:3] din;

reg s0;

reg s1;


41

// Outputs

wire y;


mux42beh uut (

.din(din),

.s0(s0),

.s1(s1),

.y(y)

);

initial

begin

din=4'b0011;

s0=1'b0; s1=1'b0;

#5 s0=1'b0; s1=1'b1;

#5 s0=1'b1; s1=1'b0;

#5 s0=1'b1; s1=1'b1;

end

initial

begin

#50 $finish;

end

endmodule

SYNTHESIS RESULTS:


42

SIMULATION RESULTS:

CONCLUSION: A 4:1 multiplexer is designed using behavioral, dataflow models are

verified using test bench.

6.2---8:1 MULTIPLEXER


43

AIM: To design a 8:1 multiplexer using behavioral ,dataflow models and verify its

functionality using the test bench. TOOLS USED: Xilinx 9.2i Hardware Tool


A multiplexer has a group of data inputs and a group of control inputs. It is also called as

data selector. The control inputs are used to select one of the data inputs and connect it to

the output terminal. A 8:1 mux has eight inputs ,3 selection lines and 1 output.

BLOCK DIAGRAM:

TRUTH TABLE:

S0 S1 S2 Y

0 0 0 Y[0]

0 0 1 Y[1]

0 1 0 Y[2]

0 1 1 Y[3]

1 0 0 Y[4]

1 0 1 Y[5]

1 1 0 Y[6]

1 1 1 Y[7]

Where S0,S1,S2 are inputs and Y is output

VERILOG CODE:


44

8:1 MUX USING DATA FLOW MODEL

`resetall

`timescale 1ns/1ps

module mux81data1(s,din,y) ;

input [0:2]s;

input [0:7]din;

output y;

wire [0:7]t;

assign t[0]=(~s[0])&(~s[1])&(~s[2]&i[0]);

assign t[1]=(~s[0])&(~s[1])&(s[2]&i[1]);

assign t[2]=(~s[0])&(s[1])&(~s[2]&i[2]);

assign t[3]=(~s[0])&(s[1])&(s[2]&i[3]);

assign t[4]=(s[0])&(~s[1])&(~s[2]&i[4]);

assign t[5]=(s[0])&(~s[1])&(s[2]&i[5]);

assign t[6]=(s[0])&(s[1])&(~s[2]&i[6]);

assign t[7]=(s[0])&(s[1])&(s[2]&i[7]);

assign y=t[0]|t[1]|t[2]|t[3]|t[4]|t[5]|t[6]|t[7];

endmodule

8:1 MUX USING BEHAVIORAL MODELING STYLE:

`resetall

`timescale 1ns/1ps

module mux81bh(i,s,o) ;

input [0:7]i;

input [0:2]s;

output o;

wire [0:7]i;

wire [0:2]s;

wire [0:7]y;

reg o;

always@(s)


45

begin

case(s)

3'b000: o=i[0];

3'b001: o=i[1];

3'b010: o=i[2];

3'b011: o=i[3];

3'b100: o=i[4];

3'b101: o=i[5];

3'b110: o=i[6];

3'b111: o=i[7];

endcase

end

endmodule

8:1 MUX TEST BENCH:

`resetall

`timescale 1ns/1ps

module mux81df_tb_v;

// Inputs

reg [0:7] din;

reg [0:2] s;

// Outputs

wire y;


mux81df uut (

.din(din),

.y(y),

.s(s)

);

initial

begin



46

din=8'b01010101;

s=3'b000;

#10 s=3'b001;

#10 s=3'b010;

#10 s=3'b011;

#10 s=3'b100;

#10 s=3'b101;

#10 s=3'b110;

#10 s=3'b111;

end

initial

begin

#100 $finish;

end

endmodule

SYNTHESIS RESULTS:


47

SIMULATION RESULTS:

CONCLUSION: A 8:1 multiplexer is designed using behavioral, dataflow models are


EXPERIMENT: 7 DEMULTIPLEXER


48

7.1. 1:4 DEMULTIPLEXER

AIM: To design a 1X4 DEMULTIPLEXER and verify its functionality and check its

simulation report.



The demultiplexer is the exact opposite to the multiplexer. In this, the data form one line

can be sent onto any one of many lines. The block diagram of multiplexer is given below

and the associated truth table.1:4 demultiplexer has one input and 4 output lines.

BLOCK DIAGRAM:

A

TRUTH TABLE:

S1 S0 Z0 Z1 Z2 Z3

0 0 A 0 0 0

0 1 0 A 0 0

1 0 0 0 A 0

1 1 0 0 0 A

VERILOG CODE FOR 1:4 DEMULTIPLEXER:

DEMULTIPLEXER

Z0

Z1

Z3

Z2

S0 S1


49

`resetall

`timescale 1ns/1ps

module demux14bh(din,s,y) ;

input [0:1]s;

input din;

output [0:3]y;

wire [0:1]s;

wire din;

reg [0:3]y;

always @(s or din)

begin

case(s)

2'b00: begin y[0]=din;y[1]=4'b0;y[2]=4'b0;y[3]=4'b0;end



2'b11: begin y[3]=din;y[1]=4'b0;y[2]=4'b0;y[0]=4'b0 ;end

endcase

end

endmodule

TEST BENCH FOR 1:4 DEMULTIPLEXER:

`resetall

`timescale 1ns/1ps

module demux14bh_tb;

// Inputs

reg din;

reg [0:1] s;

// Outputs

wire [0:3] y;



50

demux14bh uut (

.din(din),

.s(s),

.y(y)

);

initial begin


din = 1;

s=2'b00;

#10 s=2'b01;

#10 s=2'b10;

#10 s=2'b11;

end

initial

begin

#50 $finish;

end

endmodule


51

SYNTHESIS RESULTS:

SIMULATION RESULTS:

CONCLUSION:

A 1:4 demultiplexer is designed and is verified using test bench.


52

7.2--- 1:8 DEMULTIPLEXER

AIM: To design a 1:8 DEMULTIPLEXER and verify its functionality and check its

simulation report.



The demultiplexer is the exact opposite to the multiplexer. In this, the data form one line

can be sent onto any one of many lines. The block diagram of multiplexer is given below

and the associated truth table.1:8 demultiplexer has one input and 8 output lines.

BLOCK DIAGRAM:

A

TRUTH TABLE:

S0 S1 S2 Y[0] Y[1] Y[2] Y[3] Y[4] Y[5] Y[6] Y[7] 0 0 0 A 0 0 0 0 0 0 0 0 0 1 0 A 0 0 0 0 0 0 0 1 0 0 0 A 0 0 0 0 0 0 1 1 0 0 0 A 0 0 0 0 1 0 0 0 0 0 0 A 0 0 0 1 0 1 0 0 0 0 0 A 0 0

DEMULTIPLEXER 1x8

Y0

Y1

Y3

Y2

S0 S1

Y5

Y4

Y6 Y7

S2


53

1 1 0 0 0 0 0 0 0 A 0 1 1 1 0 0 0 0 0 0 0 A

VERILOG CODE FOR 1:8 DEMUX: `resetall

`timescale 1ns/1ps

module demux18beh(din, s, y);

input din;

input [0:2] s;

output [0:7] y;

// reg din;

// reg [0:2] s;

wire din;

wire [0:2] s;

reg [0:7]y;

always@(s)

begin

case (s)

3'b000:y=8'b10000000;

3'b001:y=8'b01000000;

3'b010:y=8'b00100000;

3'b011:y=8'b00010000;

3'b100:y=8'b00001000;

3'b101:y=8'b00000100;

3'b110:y=8'b00000010;

3'b111:y=8'b00000001;

default:y=8'b11111111;

endcase

end

endmodule


54

TEST BENCH FOR 1:8 DEMULTIPLEXER:

`resetall

`timescale 1ns/1ps

module demux18beh_tb_v;

reg din;

reg [0:2] s;

// Outputs

wire [0:7] y;


demux18beh uut (

.din(din),

.s(s),

.y(y)

);

initial

begin

din=1;

s=3'b000;

#5 s=3'b001;

#5 s=3'b010;

#5 s=3'b011;

#5 s=3'b100;

#5 s=3'b101;

#5 s=3'b110;

#5 s=3'b111;

end

initial

begin

#80 $finish;

end


55

endmodule

SYNTHESIS RESULTS:

SIMULATION RESULTS:

CONCLUSION:

A 1:8 demultiplexer is designed and is verified using test bench.


56

EXPERIMENT: 8 COMPARATORS

4- BIT COMPARATOR

AIM: To design a four bit comparator using behavioral model and verify using the

functionality using test bench.

TOOLS USED: Xilinx 9.2i.Hardware Tool.


Comparator is a circuit which compares two n-bit binary numbers and determines if they

are equal or which one is larger if they are not equal.

BLOCK DIAGRAM:


57

TRUTH TABLE:

a b altb aeqb agtb

0000 1111 1 0 0

0001 1110 1 0 0

0010 1101 1 0 0

0011 1100 1 0 0

0100 1011 1 0 0

0101 1010 1 0 0

0110 1001 1 0 0

0111 0111 0 1 0

1000 1000 0 1 0

1001 0110 0 0 1

1010 0101 0 0 1

1011 0100 0 0 1

1100 0011 0 0 1

1101 0010 0 0 1

1110 0001 0 0 1

1111 0000 0 0 1

Where aeqb denotes a equals b and altb denotes a less than b and agtb denotes a greater

than b

VERILOG CODE:

`resetall


58

`timescale 1ns/1ps

module comparator1(a, b, altb, aeqb, agtb);

input [0:3] a;

input [0:3] b;

output altb;

output aeqb;

output agtb;

//wire a[0:3];

//wire b[0:3];

reg altb,aeqb,agtb;

always@(a or b)

begin

if(a<b)

begin

altb=1'b1;

{aeqb,agtb}=1'b0;

end

else if(a==b)

begin

aeqb=1'b1;

{altb,agtb}=1'b0;

end

else

begin

agtb=1'b1;

{aeqb,altb}=1'b0;

end

end

endmodule

4 BIT COMPARATOR TEST BENCH

`resetall


59

`timescale 1ns/1ps

module comparator_tv_v;

// Inputs

reg [0:3] a;

reg [0:3] b;

// Outputs

wire altb;

wire aeqb;

wire agtb;


comparator1 uut (

.a(a),

.b(b),

.altb(altb),

.aeqb(aeqb),

.agtb(agtb)

);

initial

begin

a=4'b0101; b=4'b0101;

#10 a=4'b0100; b=4'b0110;

#10 a=4'b1010; b=4'b0011;

end

initial

begin

#30 $finish;

end

endmodule


60

SYNTHESIS RESULTS:

SIMULATION RESULTS:


61

CONCLUSION: A 4- bit comparator is designed and its functionality is verified using

the test bench

\

EXPERIMENT: 9 ARITHMETIC AND LOGIC UNIT

AIM: To design all the logic ALU using the behavioral modeling style and verify the

functionalities along with their synthesis and simulation reports.



Arithmetic logic unit is used to perform all the arithmetic operations like

Addition, Subtraction, division, multiplication etc and logical operations like AND, OR,

NOR, NAND, XOR, XNOR etc.

VERILOG CODE:

`resetall `timescale 1ns/1ps module alu4(a, b, s, y); input [3:0] a; input [3:0] b; input [1:0] s; output [3:0] y; wire [3:0]a; wire [3:0]b; wire [3:0]s; reg [3:0]y; always@(s) begin case(s) 2'b00:y=b; 2'b01:y=a+b; 2'b10:y=a|b; 2'b11:y={b[2:0],1'b0}; endcase end endmodule


62

TEST BENCH FOR ALU:

`resetall `timescale 1ns/1ps module alu_tb_v; // Inputs reg [3:0] a; reg [3:0] b; reg [3:0] s; // Outputs wire [3:0] y; // Instantiate the Unit Under Test (UUT) alu4 uut ( .a(a), .b(b), .s(s), .y(y) ); initial begin a=4'b0000; b=4'b0001; s=2'b00; #10 s=2'b01; #10 s=2'b10; #10 s=2'b11; end initial begin #100 $finish; end endmodule


63

SYNTHESIS RESULTS:


64

SIMULATION RESULTS:

CONCLUSION: ARITHEMETIC AND LOGIC UNIT is designed in behavioral model and output is



65

EXPERIMENT: 10 D-FLIP FLOP

AIM: To design a D-flip flop with synchronous reset in behavioral model and testing the

functionality using test bench TOOLS USED: Xilinx 9.2i Hardware Tool.


The flip flop circuit can maintain a binary state indefinitely (as long as the power is

delivered to the circuit) until directed by an input signal to switch states. The major

difference among the various types of the flip flops are in the number of inputs they

possess and in the manner in which the inputs affect the binary states. A D- flip flop has

one input D ,the input D is sampled during the occurrence of the clock pulse. In D-flip

flop with synchronous reset, the output depends only on the clock..

BLOCK DIAGRAM:

TRUTH TABLE:

Clk Q D Q(n+1)

1 0 0 0


66

1 0 1 1

1 1 0 0

1 1 1 1

VERILOG CODE:

`resetall `timescale 1ns/1ps module dff1(data, clk, reset, q); input data; input clk; input reset; output q; wire data,clk,reset; reg q; always @ ( posedge clk ) if (reset) begin q <= 1'b0; end else begin q <= data; end endmodule

TEST BENCH:

`resetall `timescale 1ns/1ps module dff1_tb_v; // Inputs reg data; reg clk; reg reset; // Outputs wire q; // Instantiate the Unit Under Test (UUT) dff1 uut ( .data(data), .clk(clk), .reset(reset),


67

.q(q) ); initial clk = 1'b1; always #5 clk = ~clk; initial begin data=1; reset=1; #5 data=0; reset=0; #5 data=1; reset=0; #10 data=1; reset=0; end initial begin #50 $finish; end endmodule SYNTHESIS RESULTS:

SIMULATION RESULTS:


68

CONCLUSION:

A D- Flip flop with synchronous reset is designed in behavioral model and tested using

test bench.

EXPERIMENT:11 SHIFT REGISTERS

11.1 LEFT SHIFT REGISTER USING ASYNCHRONOUS RESET

AIM: To design a 4-bit left shift register using asynchronous reset in behavioral model

and testing the functionality using test bench.



The Shift registers are a type of sequential circuits mainly used for the storage of the data,

a shift register is a group of flip flops connected in a chain so that the output of one flip

flop is connected as the input to the next flip flop. All the flip flops are driven by a global

clock, left shift register is shift register in which the data keeps shifting towards the left

for each positive edge of the clk

BLOCK DIAGRAM:

TRUTH TABLE:

Clk Reset Q Ser

Qa Da A

Qb Db B

Qd Db D

Qc Dc C

q

clk

Ser


69

0 1 0000 0

1 0 0001 1

1 0 0011 1

1 0 0111 1

1 0 1111 1

VERILOG CODE:

4-BIT LEFT SHIFT REGISTER WITH ASYNCHRONOUS RESET USING

BEHAVIORAL MODEL

`resetall

`timescale 1ns/1ps

module leftshiftreg(clk, reset, sr, q);

input clk;

input reset;

input sr;

output [3:0] q;

wire reset,sr,clk;

reg [3:0] q;

always@(posedge clk)

begin

if(reset)

q=4'b0000;

else

q={q[2:0],sr};

end

endmodule

4-BIT LEFT SHIFT REGISTER TEST BENCH

`resetall

`timescale 1ns/1ps

module leftshiftreg_tb_v;


70

// Inputs

reg clk;

reg reset;

reg sr;

// Outputs

wire [0:3] q;


leftshiftreg uut (

.clk(clk),

.reset(reset),

.sr(sr),

.q(q)

);

initial

clk=1'b1;

always

#5 clk=~clk;

initial

begin

reset=1'b1;

#3 reset=1'b0;

#6 reset=1'b0;

end

initial

begin

sr=1'b0;

#10 sr=1'b1;

#10 sr=1'b1;

#10 sr=1'b1;

#10 sr=1'b1;

#10 sr=1'b1;


71

#10 sr=1'b1;

end

initial

begin

#100 $finish;

end

endmodule

SYNTHESIS RESULTS:

SIMULATION RESULTS:

CONCLUSION:

A 4-bit shift register using asynchronous reset is designed in behavioral model and tested

using test bench.


72

EXPERIMENT:12 UNIVERSAL SHIFT REGISTER

AIM: To design UNIVERSAL SHIFT REGISTER and verify the functionalities along

with their synthesis and simulation reports.


DESCRIPTION OF THE MODULE: The UNIVERSAL SHIFT REGISTER(USR)

performs hold value, shift left, shift right and load value functions. This register can be

used as a serial in-serial out, parallel in –parallel out, serial in-parallel out, parallel in

serial out shift register.

BLOCK DIAGRAM:

clock

reset

leftsh

rightsf

pin

VERILOG CODE USING BEHAVIORAL MODELING: `resetall

Universal Shift register

q


73

`timescale 1ns/1ps

module universalshiftreg(clk, reset, leftsh, rightsf, sel, pin, q);

input clk;

input reset;

input leftsh;

input rightsf;

input [0:1]sel;

input [0:3] pin;

output [0:3] q;

wire clk,sel,leftsh,rightsf,reset;

wire [0:3] pin;

reg [3:0] q;

always@(posedge clk )

begin

if (reset)

q=4'b0000;

else

begin

case(sel)

2'b00:q=4'b0000;

2'b01:

q={q[2:0],leftsh};

2'b10:

q={rightsf,q[3:1]};

2'b11:

q=pin;

endcase

end

end

endmodule

USR TEST BENCH:


74

`resetall

`timescale 1ns/1ps

module universalshift_tb_v;

// Inputs

reg clk;

reg reset;

reg leftsh;

reg rightsf;

reg [0:1] sel;

reg [0:3] pin;

// Outputs

wire [3:0] q;


universalshiftreg uut (

.clk(clk),

.reset(reset),

.leftsh(leftsh),

.rightsf(rightsf),

.sel(sel),

.pin(pin),

.q(q)

);

initial

clk=1'b1;

always

#5 clk=~clk;

initial

begin

reset=1'b1;

#5 reset=1'b0;

end


75

initial

begin

leftsh=1'b1;

#5 rightsf=1'b1;

#10 pin=4'b1010;

end

initial

begin

sel=2'b00;

#5 sel=2'b01;

#5 sel=2'b10;

#5 sel=2'b11;

end

initial

#50 $finish;

endmodule

SYNTHESIS RESULTS:


76

SIMULATION RESULTS:


77

CONCLUSION: UNIVERSAL SHIFT REGISTER is designed in Behavioral model and

tested using test bench.

EXPERIMENT:13 COUNTERS


78

12.1 UP COUNTER

AIM: To design UP COUNTER and verify functionality along with its synthesis and

simulation reports.


DESCRIPTION OF THE MODULE: A sequential circuit that goes through a

prescribed sequence of states upon the application of input pulses is called counter. If a

counter counts from lower value to higher value then it is known as UP COUNTER.

BLOCK DIAGRAM:

clock

reset

enable

TRUTH TABLE:

Clock Reset Enable q

1 1 X 0000

2 0 1 0001

3 0 1 0010

4 0 1 0011

5 0 1 0100

6 0 1 0101

7 0 1 0110

8 0 1 0111

9 0 1 1000

10 0 1 1001

VERILOG CODE USING BEHAVIORAL MODELING:

`resetall

Up counter

q


79

`timescale 1ns/1ps

module upcounter(clk, reset, enable, q);

input clk;

input reset;

input enable;

output [0:3] q;

wire clk,reset,enable;

reg [0:3] q;


begin

if(reset==1'b1)

q=4'b0000;

else if(enable==1'b1)

begin

q=q+4'b0001;

end

end

endmodule

UPCOUNTER TEST BENCH: `resetall

`timescale 1ns/1ps

module upcounter_tb_v;

// Inputs

reg clk;

reg reset;

reg enable;

// Outputs

wire [0:3] q;


upcounter uut (

.clk(clk),


80

reset(reset),

.enable(enable),

.q(q)

);

initial

clk=1'b1;

always #5 clk=~clk;

initial

begin

enable=1'b1;

reset=1'b1;

#5 reset=1'b0;

end

initial

begin

#160 $finish;

end

endmodule

SYNTHESIS RESULTS:


81

SIMULATION RESULTS:

CONCLUSION: UP COUNTER is designed using behavioral modeling style and is


13.2 DOWN COUNTER


82

AIM: To design DOWN COUNTER and verify functionality along with its synthesis and

simulation reports.


DESCRIPTION OF THE MODULE: A sequential circuit that goes through a

prescribed sequence of states upon the application of input pulses is called counter.

DOWN COUNTER counts from higher value to lower value.

BLOCK DIAGRAM:

clock

reset

enable

TRUTH TABLE:

clock reset enable q

1 1 X 1111

2 0 1 1110

3 0 1 1101

4 0 1 1100

5 0 1 1011

6 0 1 1010

7 0 1 1001

8 0 1 1000

9 0 1 0111

10 0 1 0110

VERILOG CODE:

Down counter

q


83

`resetall

`timescale 1ns/1ps

module downcounter(clk, enable, reset, q);

input clk;

input enable;

input reset;

output [0:3] q;

wire enable,clk,reset;

reg [3:0]q;


begin

if(reset)

q=4'b1111;

else if(enable==1'b1)

q=q-4'b0001;

end

endmodule

DOWN COUNTER TEST BENCH:

`resetall

`timescale 1ns/1ps

module downcounter_tb_v;

// Inputs

reg clk;

reg enable;

reg reset;

// Outputs

wire [3:0] q;


downcounter uut (

.clk(clk),


84

.enable(enable),

.reset(reset),

.q(q)

);

initial

clk=1'b1;

always #5 clk=~clk;

initial

begin

enable=1'b1;

reset=1'b1;

#5 reset=1'b0;

end

initial

begin

#300 $finish;

end

endmodule

SYNTHESIS RESULTS:


85

SIMULATION RESULTS:

CONCLUSION: DOWN COUNTER is designed using behavioral modeling style and is


Verilog Code

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